The present invention relates to a method for transmitting user data messages, from a sender to one or more recipients, a subscriber device and a radio communication system.
In the case of many services and applications which are offered in modem mobile radio systems, messages must be transmitted to not just one subscriber, but to two or more subscribers. Such services and applications include, for example, news groups, video conferences, video on demand, distributed applications, etc.
When transmitting the messages to the different subscribers, it is possible to send a copy of the data to each recipient separately. Although this technique is easy to implement, it is unsuitable for large groups. Because the same message is transmitted over N individual connections or unicast connections (N corresponds to the number of recipients) and is therefore sent multiple times over shared connection paths, this method requiring a very high bandwidth.
A more advantageous possibility is offered by multicast (group call) transmission. Here, the different subscribers to whom the same message is to be transmitted are combined into a multicast group, and the multicast group is assigned an address which is specifically known as a multicast address. The data which must be transmitted is only sent once to this multicast address accordingly. In an ideal case, the multicast message is sent only once over shared connection paths from the sender to the recipients. It is not necessary for the sender to know where and how many recipients are hiding behind the multicast address.
In the case of broadcast (collective call), messages are sent to all subscribers within a geographical area. Such an area can be specified as a part of the overall network, for example. As in the case of multicast, the broadcast message is ideally sent only once over shared connection paths from the sender to the recipients. Each subscriber must implement enabling settings at the local terminal if the subscriber wishes subsequently to analyze broadcast packets from a corresponding broadcast group. In this way, individual subscribers can specify whether they wish to receive or discard all broadcast messages, or whether they wish to receive specific messages only.
As part of a known method for data communication, a specific quantity of frames is typically always exchanged between a network and a mobile radio device within a specific time. In this case, a frame is a time-relative structure, upon which in a UMTS (Universal Mobile Telecommunications System), for example, the entire signal processing and data transmission is based, see [2].
If all these frames are continuously transmitted and received by the mobile radio device, this is known as continuous transmission or continuous reception. However, it is also possible during the transmission to use an interrupted (discontinuous) reception, namely Discontinuous Reception DRX, in order to reduce the energy requirements of the mobile radio devices, for example. When using DRX, the frames are not continuously transmitted and received by the mobile radio devices, but specific frames are omitted. In this mode, however, at least a specific subset of all frames or a subset of the possible frames must be transmitted in order to maintain the connection.
In the context of transmitting messages or data to various subscribers, it is now also conceivable to provide for a transmission of messages having multimedia content. A problem may arise here, however, in that not all data types of transmitted multimedia messages can be processed by every subscriber device. In this case, it is then possible for a subscriber device to use resources and energy for receiving specific multimedia messages containing audio and video data, and for it then to transpire when processing the messages that the subscriber device is not designed to process or playback video data at all. In such a case, energy is wasted for no purpose and the service life of the subscriber device is reduced.
The present invention is therefore directed toward a way of providing an efficient, resource-saving, energy-saving transmission of data or messages to one or more recipients of a point-to-multipoint service.